The problem with ammunition recovery is not merely about them being broken and hence unusable.
It seems that ammunition breakage is baked in to ammunition recovery after a fight, and that an unbreakable arrow would improve the recovery rate somehow, but RAW is RAW.
As a sometimes-archer I lost a few arrows from target practice simply by shooting the target, missing and them embedding themselves into medium high grass is such a fashion that I simply was unable to retrieve it. I knew where I shot at, I combed the grass - but still no arrow to be found (RealLife Expertise - might not transfer 100% over).
Should be the same in a fight, sometimes the darned thing just can't be found afterwards so no reason to give someone using unbreakable arrows a higher retrieval chance.
As for unbreakable arrows usages beside being used as ammunition:
- use as a lightweight prybar
- combine with 2 ropes for a ladder (use as ladder steps)
- use 3-4 of them for a more silent (aka wooden) climbing hook
- use as throw-stick for your companion wolf (won't be chewed up)
Outside of RAW:
As a DM I would grant you a chance of retrieving broken arrows if you use f.e. Detect Magic
For the duration, you sense the presence of magic within 30 feet of you. If you sense magic in this way, you can use your action to see a faint aura around any visible creature or object in the area that bears magic, and you learn its school of magic, if any.
The spell can penetrate most barriers, but it is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt.
because of them not getting broken and hence unusable - so the only factor for retrieving them would be to actually find them.
Chances of finding them would depend on the combat and environment situation, examples:
- lower for a ship to ship shooting: don't hit something and they may go overboardnd sink
- lower for ballistic kind of shooting: it is harder to guess where it would have hit
- higher for indoor/cave situation in some kind of confined space
Ambient magic might also influence chance: areas with no ambient magic might make it easier to detect the glow, areas with high ambient magic make it harder.
With Detect Magic and ammo retrieval loosing an arrow would be more of a "item drain" or advenure hook.